Injector impinger

ABSTRACT

A sterilizing system for receiving a stream of solid-stabilizer-containing fluid and sterilizing an article comprises a chamber for receiving the article and an injection assembly coupled to the chamber for generating and introducing a fluid jet into the chamber. The system particularly comprises an injector impinger for removing particulates and liquid droplets from the solid-stabilizer-containing fluid by causing a sudden change of the stream line direction of the fluid jet. The injector impinger is positioned between the injection assembly and the article, so that the fluid jet can not reach the article without first interacting with the injector impinger. A method for removing particulates from a solid-stabilizer-containing fluid in a sterilizing process comprises the steps of providing the fluid, vaporizing the fluid, forming a vapor stream from the vaporized fluid, and removing the particulates and the droplets from the vapor stream by causing a sudden change of direction of stream line of the vapor stream.

RELATED APPLICATIONS

This application claims the benefit of the Provisional Application No.60/050983, entitled INJECTOR IMPINGER, filed Jun. 23, 1997.

BACKGROUND OF THE INVENTION

The present invention relates to a system for injecting or dispensingcontrolled volumes of fluid, particularly for automated injections ofvery small amounts of fluid into a chamber for sterilizing items such asmedical instruments. The present invention particularly relates to asystem for removing particulates from the injected fluid and preventingthe particulates from depositing on surfaces of the items to besterilized.

Various sterilants or sterilizing fluids have been used to sterilizemedical instruments. One effective way of sterilization is to sterilizethe item with a sterilant vapor. In this sterilization process, the itemto sterilized is placed in a vacuum chamber. A liquid sterilant isintroduced into the vacuum chamber and vaporized therein, so that theitem is sterilized by the sterilant vapor.

U.S. Pat. No. 4,643,876 discloses a sterilization method and apparatus.In this method, a sterilizing agent such as hydrogen peroxide isintroduced into an evacuated sterilizing chamber where it is vaporizedand allowed to disperse onto the items to be sterilized. After a desiredperiod of time, electrical energy is then applied in the chamber toionize the gas to form a plasma at a power level sufficient to achievesterilization.

U.S. Pat. No. 4,938,262 and U.S. Pat. No. 4,913,196 issued to the sameinventors disclose a pumping apparatus for the fluid injection in asterilization system, and a method of pumping a sterilizing liquid intoan evacuated sterilizing chamber containing an article to be sterilized.

The pumping apparatus for the fluid injection system disclosed in U.S.Pat. No. 4,938,262 provides a fluid supply in the form of a prepackagedclosed cell containing a known volume of fluid. The apparatus furtherincludes a mechanism for receiving and positioning the cell, and a cellopener assembly cooperating with the mechanism for penetrating the cellto form an outlet from the cell. A device cooperating with the cell andthe receiving mechanism forces the entire volume of fluid out of thecell, thus providing a convenient pumping apparatus for providing aknown quantity of fluid.

The systems provided in the above U.S. patents are effective, and havenumber of advantages over other known systems. Consequently, thosesterilization systems disclosed in the above mentioned U.S. patents havebeen commercialized.

However, further improvements are needed to overcome the disadvantagesof the existing vapor sterilization systems. One common problem ofexisting vapor sterilization system is the deposition of particulates onthe surface of the item to be sterilized because stabilizers present inthe liquid sterilant, which gives the sterilized item unpleasant andunclean appearance.

Thus, there is a need for a method and apparatus, which eliminates thedeposited particulates on the surface, and meanwhile maintainssterilization efficiency.

SUMMARY OF THE INVENTION

The present invention presents a significant improvement to existingsterilization systems, especially those described in U.S. Pat. No.4,643,876, 4,938,262, and 4,913,196 by eliminating or significantlyreducing particulate deposition on surfaces of items to be sterilized.These two U.S. patents are incorporated herewith by reference in theirentirety.

The present invention provides a simple and economical way to removeparticulates from a fluid stream before it reaches the article to besterilized and significantly reduce the solid residue deposition onsurface of the article to be sterilized. According to the presentinvention, an injector with a special impinger is provided. The impingeris placed across the pathway of sterilizing fluid stream injected froman inlet of the injector. Before reaching to the impinger a significantportion of the liquid sterilant should be vaporized so that a vaporstream of the sterilant is generated. The impinger provides a surface ofsuitable shape facing the vapor stream at an appropriate angle. When thestream of the sterilant vapor approaches the impinger surface, thestream line will change direction sharply near the impinger surface.During the vaporizing process, stabilizers or other solid additivesinitially dissolved in the liquid sterilant will be separated from thefluid phase as tiny particulates and travel with the vapor stream.Because their mass, those particulates will not be able to follow thestream line when the stream line takes a sharp turn near the impingersurface. Instead, those particulates will keep moving toward theimpinger surface and are collected on the impinger surface. Thecollecting efficiency can be affected by many factors, such asdimension, shape, roughness, or material of the impinger surface, theangle between the impinger surface and the stream line, the velocity ofthe stream, the vapor/liquid ratio of the stream.

One aspect of the present invention relates to a sterilizing system forreceiving a stream of solid-stabilizer-containing fluid and sterilizingan article. The sterilizing system comprises:

a chamber, which may further comprise an electrode for generatingplasma;

an injection assembly connected to the chamber sealed and normallyclosed so that a vacuum may be maintained in the chamber;

an injector impinger having an surface, mounted inside the chamber andpositioned between the injection assembly and the article.

The injection assembly has a body, a fluid inlet passage, a vaporizerbowl, a vapor passage for introducing vapor from the vaporizer bowl tothe chamber and forming a vapor jet, and a male thread at the bottomportion of the injection assembly. The injection assembly furthercomprises a heating device secured to its body.

The injector impinger has a conically-shaped central section, a disksection surrounding said conically-shaped section, and a hole with afemale thread in the center of the injector impinger, and is secured tosaid injection assembly through said male and female threads so that theupper surface of the disk section of the injector impinger issubstantially perpendicular to the stream line of the vapor jet andprevents the vapor jet from directly impinging the article. The injectorimpinger is made of plasma compatible materials, such as polypropylene.

The fluid agent can be any compound suitable for sterilization.Preferably, the fluid agent is liquid hydrogen peroxide, morepreferably, is substantially pure hydrogen peroxide. Any solidstabilizer suitable for hydrogen peroxide can be used. A very effectivesolid stabilizer used in this invention is purchased from FMC.

Another aspect of the present invention provides a method for removingparticulates from a solid-stabilizer-containing fluid in a sterilizingprocess. The method comprises the steps of:

introducing a liquid phase fluid containing dissolved solid stabilizer;

vaporizing said liquid phase fluid forming a vapor stream containingparticulates mainly formed from the solid stabilizer;

removing the particulates from the vapor stream and entrained liquiddroplets by sudden change of direction of stream line of said vaporstream.

The vaporizing step is conducted in a chamber under vacuum of about 0-1torr, preferably 0-400 mtorr, before the liquid is injected into thechamber, and at a temperature in the range of about 20-70 C.

The step of removing particulates is conducted by putting an injectorimpinger between the vapor stream and a downstream article to besterilized, so that the vapor stream can not reach the article withoutimpinging the injector impinger first. Preferably, the injector impingeris positioned so that the stream line of the vapor stream issubstantially perpendicular to the injector impinger's surface facingupstream in terms of the travel direction of the vapor stream.

Another aspect of the present invention provides an injector impingerfor removing particulates from a fluid stream introduced into asterilization system, said sterilization system comprising a fluidinjection assembly, a sterilizing chamber for holding vacuum, anelectrode installed in the chamber for generating plasma, and an articleto be sterilized within the chamber. The injector impinger comprises:

a base plate positioned between the injection assembly and the article;

a connecting device for securing the injector impinger in position.

The base plate has a conically-shaped central section and a flat disksection surrounding the central section, and the connecting device is athreaded through hole positioned in the center of the base plate. Theinjector impinger is made of plasma compatible materials, preferably,plastic material such as polypropylene.

Still another aspect of the present invention provides a liquidinjection combination for vaporizing injected liquid and removingparticulates from generated vapor from the injected liquid. Thecombination comprises:

a liquid inlet for receiving the injected liquid;

a vaporizer bowl for vaporizing the injected liquid;

a vapor passage providing a passage for vapor generated from theinjected liquid and forming a vapor stream;

a injector impinger having a surface positioned against stream line ofthe vapor stream, so that particulates traveling with the vapor streamand entrained liquid droplets are separated from the vapor stream andretained on the surface of the injector impinger.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of the sterilizing system illustrating thesystem of the present invention;

FIG. 2 is a cross-sectional view of the injection assembly connected tothe injector impinger in the sterilizing system of the presentinvention;

FIG. 3 is a schematic view of the injector impinger of the presentinvention;

FIG. 4 is a isometric view of the injector impinger of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The existing sterilizing systems using liquid hydrogen peroxide assterilant, such as those described in the U.S. patents cited above, arevery effective. However, a stabilizer is usually added to the hydrogenperoxide during its storage to stabilize the hydrogen peroxide, and mostsuch stabilizers are in solid state. When used, the solid stabilizers isdissolved in hydrogen peroxide, and the liquid hydrogen peroxide withdissolved stabilizer is injected into a sterilizing chamber where theliquid hydrogen peroxide or its solution is vaporized under vacuumand/or elevated temperature. During this vaporizing process, thedissolved solid stabilizer separates from the liquid phase and formstiny particulates traveling with the vapor stream and with anyincompletely vaporized liquid droplets generated from the injectedliquid hydrogen peroxide, and deposits on the surfaces of articles to besterilized in the sterilizing chamber. The deposition of the solidstabilizer residue on the article surface is very undesirable, becauseit presents an unsightly product image to hospital personnel.

Referring to FIG. 1, there is schematically illustrated a cylindricalchamber 10 having a door 12 on one end. The chamber is connected to asuitable vacuum source by way of a conduit 14. The chamber is adapted toreceive items to be sterilized, such as surgical instruments, inaccordance with a method outlined in U.S. Pat. No. 4,643,876 which isincorporated herewith by reference, wherein a liquid such as hydrogenperoxide is introduced into the chamber. For delivering such fluid, inaccordance with the present invention, there is provided a fluidinjection system 16 positioned adjacent to the chamber 10.

The system includes a cassette or cartridge 18 containing the fluid tobe injected, a cassette receiving, positioning and clamping mechanism20, and a fluid injector valve assembly 22 mounted on and interconnectedwith the chamber. An injector impinger 200 (not shown) is secured to thefluid injector valve assembly 22 or to other part of the chamber. Thefluid injector system 16 can be thought of as a pump in which thecassette 18 is inserted into the cassette receiving mechanism 20 anddoses of the media contained in the cassette are automatically injectedinto the chamber during automated sterilizing cycles.

The system described above is similar to the system disclosed in U.S.4,938,262 which is incorporated herewith by reference, except for theaddition of an injector impinger. The significant advantage of thesystem of the present invention results from the addition of theinjector impinger 200 inside the chamber. For example, the injectorimpinger can be positioned at the vapor outlet of the fluid injectorvalve assembly 22 with or without modifications to the structure of thefluid injector valve assembly 22.

Other modifications on the system of U.S. Pat. No. 4,938,262, inaddition to the introduction of an injector impinger, are made in thepresent invention. Thus, in one preferred embodiment of the presentinvention, the fluid injector valve assembly 22 is replaced by aninjection assembly 22b as shown in FIG. 2. The sterilizing chamber ofthe present invention may also further include an electrode forgenerating plasma, and has a rectangular cross-sectional area or anyother appropriate shape.

In one preferred embodiment, the injection assembly 22b is mounted andsealed to the chamber 10. The injection assembly 22b can be furtherprovided with a pressure relief valve connecting to a liquid injectiondevice. As shown in FIG. 2, the injection assembly 22b has an body 100which is mounted and sealed to the chamber 10. A valve outlet passage102 for receiving liquid hydrogen peroxide or other fluid from a liquidinjection device such as that shown in FIG. 1. An 0-ring seal 104 isprovided to secure the sealing around the valve outlet passage 102. Thevalve outlet passage intrudes into a vaporizer bowl 106 where theinjected liquid is vaporized. The vaporizer bowl is defined by the body100 and a second piece 108. The valve outlet passage 102 is also locatedat the center of the second piece 108. Vapor passage 110 is provided toconnect the vaporizer bowl 106 to the chamber 10. Vapor generated fromthe injected liquid in the vaporizer bowl 106 travels through the vaporpassage 110 from the vaporizer bowl 106 to the chamber 10 and forms avapor stream or vapor jet together with solid stabilizer residueparticulates and entrained liquid droplets. At the bottom portion of thebody 100, there is an extrusion part with a male thread 112 forreceiving the injector impinger. The injection assembly is also equippedwith a heating device (not shown) for keeping a desired temperature atthe vaporizer bowl 106 and the valve outlet passage 102. The operationtemperature may vary, preferably in a range of about 20-80, morepreferably about 55-65° C.

An injector impinger 200 is attached to the injection assembly as shownin FIG. 2. Referring to FIGS. 3 and 4, the injector impinger has aconically-shaped central section 202, a flat disk section 204surrounding the conically-shaped section 202, and a downward extrusionpiece 205 in the center with an elongated hole 206 and a female thread208 on the inner wall of the elongated hole 206. The injector impinger200 is secured to the body 100 through the male thread 112 of the body100 and the female thread 208 of the injector impinger 200. Ifdesirable, the injector impinger can be provided with a temperaturecontrol mechanism to control its temperature. For example, the injectorimpinger can be made hollow, and cooling or warming fluids are filledinto or circulated through the hollow body of the injector impinger.

The vapor stream together with the solid stabilizer residue particulatesand entrained liquid droplets enters the chamber 10 through the vaporpassage 110, forming a vapor stream or vapor jet. The vapor jet travelsat a velocity determined by several factors including the dimension ofthe vapor passage 110, the pressure drop between the vaporizer bowl 106and the chamber 10, and the temperature of the vapor jet. The vapor jetvelocity will change as the vapor jet travels away from the outlet ofthe vapor passage.

Although the present invention is not limited to any theory, it isbelieved that the particulate removing mechanism of the presentinvention is based on fluid dynamic principles. Thus, when the vapor jetis entering the chamber 10 from the outlet of the vapor passage, thevapor entrained liquid droplets and the tiny particulates travel alongstraight stream lines at certain velocity. Once the vapor jet isdisturbed by an object, the stream line 210 of the vapor jet will changedirection as shown in FIG. 3 according to the shape of the surface ofthe object. Because of their mass, the particulates and entrained liquiddroplets can no longer follow the stream line 210. Instead, theparticulates and entrained liquid droplets will travel along a path 212between the straight stream line and the changed curved stream line 210,and impinge the surface of the injector impinger 200. The particulateswill stick to the surface of the injector impinger. Apparently, velocityof the vapor jet is an important factor affecting particulate removingefficiency. Thus, the distance between the particulate-collectingsurface of the injector impinger and the outlet of the vapor passagewill affect particulate-removing efficiency. The shape of theparticulate-collecting surface and the angle between the stream line andthe surface also have important effects. Preferably, theparticulate-collecting surface is positioned perpendicular to the streamline.

Other options are obvious based on the teaching of the presentinvention. For example, the injector impinger does not have to be asingle piece, does not have to be mounted to the injection assembly 22b,and does not have to be the shape as described earlier. The vaporpassage 110 does not have to be vertical. In stead, it can be directedto the side wall of the chamber 10, and the particulates are collectedin an injector impinger accordingly positioned. The injector impingercan be made of any metal, ceramic, and plastic materials. However, ifthe injector impinger is used with plasma, it should be made ofplasma-compatible materials such as plastics. In a preferred embodimentof the present invention, the injector impinger is made ofpolypropylene.

In the use of the system of the present invention, vacuum is applied tothe chamber 10 by way of the conduit 14. And the pressure in the chamber10 and the vaporizer bowl 106 is preferably kept below about 1 torr,more preferably between about 0-400 mtorr before the liquid agent isinjected. Then, a liquid agent such as hydrogen peroxide with dissolvedsolid stabilizer such as FMC is injected into the vaporizer bowl throughvalve outlet passage 102. The liquid injection assembly described inU.S. Pat. No. 4,913,196 can be used to make the injection. In order tofacilitate the evaporation of the liquid agent, vaporizer bowl 106 ofthe injection assembly 22b can be heated to a desired temperature,preferably 20-80° C., more preferably 50-70° C. In one preferredembodiment, the vaporizer bowl is heated to 60° C. The generated vaporstream flows from the vaporized bowl to the chamber 10 through vaporpassage 110 under a pressure drop between the vaporizer bowl 106 and thechamber 10. The pressure drop is caused by the rapid evaporation of theliquid agent. The vapor stream with solid stabilizer particulates andentrained liquid droplets impinges the upper surface of the injectorimpinger 200. A significant percentage of the particulates will beseparated from the vapor stream and collected on the surface. As thevapor stream continue to travel along a stream line affected or confinedby the injector impinger, a portion of the particulates also continue tofollow the vapor stream. In the preferred embodiment shown in FIG. 2,the stream line of the vapor stream will follow the wall of the chamber10 after impinging the injector impinger 200. Thus, the remaining solidstabilizer particulates will deposit on the walls and bottom of thechamber. After certain cycles of sterilizing operation, the injectorimpinger can be easily replaced and cleaned. The walls and the bottom ofthe chamber 10 are also easy to clean. Therefore, the particulatedeposition on surfaces of the items to be sterilized is eliminated or atleast significantly reduced.

While the invention for removing particulates from a fluid has beendescribed in connection with injecting liquid into a chamber for asterilizing cycle, it should be understood that the system is alsouseful for removing particulates from a liquid to be injected in aprocess other than sterilization. Also, the system can be used to removeparticulates from a gas or mist injected into containers other thanvacuumized chambers. Various modifications can be made without departingfrom the spirit and scope of the present invention.

What is claimed is:
 1. A sterilizing system for receiving a stream offluid containing solid particulates and sterilizing an articlecomprising:a chamber for receiving the article; an injection assemblycoupled to the chamber for generating and introducing a fluid jet intosaid chamber; and an injector impinger positioned between said injectionassembly and the article, so that the fluid jet can not reach thearticle without first interacting with the injector impinger, whereinsaid injector impinger is located outside said injection assembly andwherein said injection assembly comprises:a fluid inlet passage forintroducing the fluid; a vaporizer bowl for vaporizing at least aportion of the fluid; and a vapor passage for introducing the at leastpartially vaporized fluid from the vaporizer bowl to the chamber andforming the fluid jet.
 2. A sterilizing system of claim 1, wherein saidvaporizer bowl is operated under a first pressure lower than atmosphericpressure, said chamber is operated under a second pressure lower thansaid first pressure.
 3. A sterilizing system of claim 1, wherein theinjector impinger has a impinging surface for interacting with the fluidjet and collecting particulates contained in the fluid jet, said surfacefaces the fluid jet and forms an angle with stream line of the fluidjet, such that direction change of said stream line caused by saidsurface is sharp enough to cause particulates unable to follow thechanged stream line and stick on said surface.
 4. A sterilizing systemof claim 3, wherein the injector impinger has a truncated cone-shapedcentral section with a hole for connecting said injection assembly, anda disk section surrounding said cone-shaped central section, said disksection provides said impinging surface substantially perpendicular tosaid stream line.
 5. A sterilizing system of claim 3, wherein theinjector impinger is made of plasma compatible materials.
 6. Asterilizing system of claim 5, wherein the injector impinger is made ofpolypropylene.
 7. A sterilizing system of claim 3, wherein the chamberfurther comprises an electrode for generating a plasma.
 8. A sterilizingsystem of claim 3, wherein the injection assembly further comprises aheating device secured to its body.
 9. A sterilizing system of claim 3,wherein the fluid jet comprises hydrogen peroxide and solidparticulates, wherein the solid particulates comprise hydrogen peroxidestabilizer.
 10. A method for removing solid particulates from fluidcontaining solid particulates in a sterilizing process, comprising thesteps of:providing said fluid; vaporizing said fluid from an injectionassembly; forming a vapor stream from said vaporized fluid, said vaporstream containing solid particulates mainly formed from a solidstabilizer and entrained liquid droplets; and removing the solidparticulates from the vapor stream by causing a sudden change ofdirection of stream line of said vapor stream with an impinger locatedoutside said injection assembly.
 11. A method of claim 10, wherein thevaporizing step is conducted under a vacuum in the range of about 0-1torr.
 12. A method of claim 10, wherein the vaporizing step is conductedat a temperature in the range of about 20-70° C.
 13. A method of claim10, wherein the step of removing the particulates and the droplets isconducted by placing an impinging surface between the vapor stream andan article to be sterilized, so that the vapor stream can not reach thearticle without impinging the impinging surface first.
 14. A method ofclaim 13, wherein the impinging surface is substantially perpendicularto stream line of the vapor stream.
 15. A method of claim 10, whereinthe solid stabilizer is a hydrogen peroxide stabilizer.
 16. A method ofclaim 10, wherein the fluid comprises hydrogen peroxide.
 17. An injectorimpinger for removing solid particulates from a fluid stream introducedinto a sterilization chamber for sterilizing an article, said fluidstream being introduced from an injector assembly, said injectorimpinger comprising:an impinging surface facing said fluid stream andpositioned upstream of the article, so that said impinging surfacecauses a sudden change of direction of stream line of the fluid streambefore said fluid stream reaches the article, wherein said impingingsurface is located outside of the injector assembly; and a connectingdevice for securing the impinging surface in position, wherein theinjector impinger is made of plasma compatible materials.
 18. Aninjector impinger of claim 17, wherein the injector impinger has atruncated cone-shaped central section and a disk section surroundingsaid cone-shaped central section, said disk section provides saidimpinging surface substantially perpendicular to said stream line, andsaid connecting device comprises a central hole in the truncatedcone-shaped central section.
 19. A sterilizing system for receiving astream of fluid containing solid particulates and sterilizing an articlecomprising:a chamber for receiving the article; an injection assemblycoupled to the chamber for generating and introducing a fluid jet intosaid chamber; an injector impinger positioned between said injectionassembly and the article, so that the fluid jet can not reach thearticle without first interacting with the injector impinger, whereinsaid injector impinger is located outside said injection assembly; and aheating device secured to a body of the injection assembly.